Multiple type constraints with generics

questionOption.swift

import UIKit

// Ref: https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Generics.html#//apple_ref/doc/uid/TP40014097-CH26-XID_292

protocol OptionView: class {
    func handleKeyCommand()
}

class QuestionView<V> where V: UIView, V: OptionView {
    private let optionView: V
    init(optionView: V) {
        self.optionView = optionView
        optionView.handleKeyCommand()
    }
}

class TermOptionView: UIView, OptionView {
    func handleKeyCommand() {
        print("normal option")
    }
}

class DiagramOptionView: UIView, OptionView {
    func handleKeyCommand() {
        print("diagram option")
    }
}

let diagramOptionView = DiagramOptionView()
let question1 = QuestionView(optionView: diagramOptionView)

let termOptionView = TermOptionView()
let question2 = QuestionView(optionView: termOptionView)